Emerging information suggests that differential expression in estrogen metabolism generates differences in health outcomes. Observations from ethnic groups, particularly comparisons of Asians and Caucasians, have precipitated both interest and controversy about differences in estrogen metabolism and health status. The goal of this application is to assess the contribution of estrogen metabolites and xenoestrogens as well as their potential signaling pathways to selected subsequent human health measures in women transitioning the menopause. We will 1) examine whether smoking and diet influence estrogen metabolism; 2) assay for both estrogens and phenolic products that contribute to the total ligand load and determine if estrogen effects on measures of health status (absolute level at follow-up or change from baseline) are misattributed because of failure to account for estrogen mimics; 3) examine the interaction between the arylhydrocarbon receptor (ArH) and ER receptors to ascertain if this interaction modifies the association of estrogens to subsequent measures of health status (absolute level at follow-up or change from baseline); and 4) use follicular and luteal phase samples, collected longitudinally across the menopausal transition, to ascertain if the relative hormone differences in the menstrual cycle segments over time are related to health outcomes. The measures of health status to be evaluated include vasomotor symptoms (hot flashes), age at menopause, measures of lipids and thrombosis and bone mineral density. This application will use Repository serum and urine samples from an existing large study of African-American, Caucasian, Chinese, Hispanic and Japanese women at the midlife [Study of Women's Health Across the Nation (SWAN)]. Additionally, SWAN can provide the longitudinal data about both smoking and diet exposures and health outcomes measures without additional data collection. This is a unique opportunity to prospectively integrate lifestyle elements with measures of hormone metabolism pathways into a comprehensive examination of multiple human health effects.